Deposition of thin films on a substrate surface is an important process in a variety of industries including semiconductor processing, diffusion barrier coatings and dielectrics for magnetic read/write heads. In the semiconductor industry, in particular, miniaturization requires atomic level control of thin film deposition to produce conformal coatings on high aspect structures. One method for deposition of thin films is chemical vapor deposition (CVD). In this process, a wafer is typically exposed to one or more volatile precursors, which react to deposit films. A related process is atomic layer deposition (ALD), which employs sequential surface reactions to form layers of precise thickness controlled at the Angstrom or monolayer level. Most ALD processes are based on binary reaction sequences which deposit a binary compound film. Because the surface reactions are sequential, the two gas phase reactants are not in contact, and possible gas phase reactions that may form and deposit particles are limited.
There is a need for new deposition chemistries that are commercially viable, particularly in the area of elemental metal films, including nickel films for nickel silicide contacts. For example, nickel films have been deposited using Ni(PF3)4 and bis(cyclopentadienyl)Ni coordination complexes. However, each of these complexes has presented problems. Ni(PF3)4 and Ni(CO)4 are toxic and bis(cyclopentadienyl)Ni can lead to carbon contamination in the film. Bis(allyl)nickel compounds are both more volatile and more reactive than the well-studied bis(cyclopentadienyl) nickel analogs, which has the potential to facilitate the metal film formation. However, bis(allyl) nickel compounds are generally too unstable for storage or clean incorporation into a deposition process. The present invention addresses these problems by providing novel chemistries.